Is this on Android? I have the up to date iOS app and can pick seats fine. Literally only downloaded the app yesterday after booking my first TG flight since 2009.
iOS. I have the same issue too for an award reservation created from United. I think if the reservation has been created from Thai - the seat selector does not have an issue showing up. However if the reservation is created from a 3rd party it seems the "Title" field is not populated and not editable - so the app or web does not allow to save the passenger details and get to the seat selector. I hope they fix this soon....